Incandescing electric lamp



(No Model.)

' T. A. EDISON.

Incandesbing Electric Lamp.

N 239 |49 Patented March 22, I881.

UNITED STATES PATENT ()FFICE.

THOMAS A. EDISON, OF MENLO PARK, NEW JERSEY.

INCANDESCING ELECTRIC LAMP.

SPECIFICATION forming part of Letters Patent No. 239,149, dated March22, 1881.

Application filed December 15, 1880.

1'0 all whom it may concern:

Be it known that I, TnoMAs A. EnIsoN, of Menlo Park, in the county ofMiddlesex and State of New Jersey, have invented anew and usefulImprovement in Incandescin g Electric Lamps; and I do hereby declarethat the following is a full and exact description of the same,reference being had to the accompanying drawings, and to the letters ofreference marked thereon.

My invention relates to incandescent electric lamps, and is intended asan improvement on the form shown in Letters Patent No. 230,255, issuedto me July 20, 1880.

In the lamp described in the above patent the glass stem through whichthe wires pass has a round bulb at the top, in which the wires aresealed, and a round enlargement below this bulb, which supports theexterior globe of the lamp. The interior of this globe being a vacuum,whiletlie interior of the inside stem is filled with air, a considerablepressure is exerted on the inner surface of the upper bulb, and thispressure is exerted on the weakest part-a concave surface. Therefore, inmy present invention, I make this bulb with adepression in its top, sothat the atmospheric pressure is exerted on a convex surface, which isless likely to be injured thereby.

In some cases, instead of a hollow spherical enlargement of the stem asa support to the globe, it may be desirable to use a solid projectionextending from the sides of the stem as a support for the globe, and towhich the globe is sealed.

My present invention, then, consists, first, in constructing the upperbulb with a concavity or depression in its top 5 and, second, in asupport for the globe formed of a projection extending laterally fromthe stem and forming a part thereof.

In the accompanying drawings, Figure 1 is (No model.)

a sectional view of an entirelamp constructed according to my invention,and Fig. 2 a sec tional view of the interior glass stem.

The dotted lines in Fig. 2 show the construction of the bulbs, aspatented by me in the above-mentioned Patent No. 230,255.

A is the exterior globe, and G the interior glass stem, through whichthe wires 1 2 of the circuit pass, being sealed in the glass where theypass through it, and terminating in the clamps c, which hold the carbon13. At (Z a bulb is blown on the stem, depressed or hollowed out at 6.At D D an enlargement is also blown on the glass; but while the glass issoft it is flattened down, and forms the projection or ring of glassshown. It is of the same width as the lower part of the globe A, whichthey support, and to which they are hermetically sealed.

Under some circumstances, and for somepurposes, this form possessesconsiderable advantages over the form before patented by me, inasmuch asthe bulb (Z is less liable to breakage, and'a better support is affordedfor the globe by the projection D D.

What I claim is- 1. In an incandescing electric lamp, thesupporting-neck formed with a concavity at the point where the leadingwires pass through and are sealed therein, substantially as set forth.

2. The supporting-neck formed with asolid glass projection, to and uponwhich the inclosingglobe is supported and sealed, substantially as setforth.

This specification signed and witnessed this 3d day of December, 1880.

THOS. A. EDISON.

Witnesses:

H. W. SEELY, S. D. Morr.

